Exhaust will not affect the way your transmission behaves, its just a muffler delete. You may be noticing the higher revs due to the louder exhaust sound.
Mine now makes me notice downshifts because of the added sound.
Dynomax muffler delete sounds a bit louder than the Borla S-Type. I have had both and switched from Borla to Dynomax since I wanted more sound
Borla S-Type will be perfect since you don't want it as loud as the Dynomax